The present invention generally relates to procedures for inspecting the condition of manufactured articles, and, more particularly to the inspection of the interiors of manufactured articles such as tanks, medical implants, turbines, and other closed applications in which only limited access is provided. This invention was made with Government support under Contract No. W-7405-ENG-36 awarded by the U.S. Department of Energy. The Government has certain rights in the invention.
Inspection of manufactured articles is of great importance, particularly to manufacturers of critical equipment whose failure can produce catastrophic results. However, some of the articles in this category defy close inspection because the geometry of the article makes inspection extremely difficult for conventional inspection techniques.
Fiber optical devices are used extensively to view objects that normally would be considered inaccessible. The optical fiber elements for this purpose are typically smaller than 50 xcexcm in diameter, including protective layers. Optical fibers such as these can be bent into radii as short as 3 cm, allowing their infiltration into areas that normally preclude direct imaging techniques.
The medical community has made extensive us of such optical fibers for endoscopic applications, such as the real-time imaging of internal organs to provide guidance for microsurgical techniques. Fiber-optic technology also has been applied in many other areas, such as opto-mechanical applications for numerous industrial and medical applications.
The primary problem with prior art, fiber optic imaging is that it is difficult to achieve acceptable measurement of surface tolerances or roughness through a single port or single optical fiber. Conventional fiber optic imaging also does not provide any quantitative measurement of the interior region being imaged. This is because prior art systems generally must rely on interferometry concepts requiring multiple fibers.
It is therefore an object of the present invention to provide profilometer apparatus for inspecting the interior surfaces of tanks and other device under tests, including medical implants and any enclosure having a single access port.
It is another object of the present invention to provide apparatus for inspecting interiors of tanks and other device under tests that is capable of accurate quantitative measurement of interior surface imperfections with a high degree of resolution.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, apparatus for inspecting the interior of a device under test through a single port in the device under test comprises laser means for producing laser energy, with beam splitter means for directing the laser energy to a first direction and to a second direction. Delay means receive the laser energy from the second direction for introducing an amount of controllable delay to the laser energy from the second direction and outputting the delayed laser energy from the second direction. Optical routing means receive the laser energy from the first direction for directing the laser energy from the first direction to ones of a first at least one optical fibers that enter the device under test through the port, and for transmitting laser energy reflected from interior surfaces of said device under test through the port, and for transmitting laser energy reflected from interior surfaces of the device under test to ones of a second at least one optical fibers. Elongate dye-cell means receive the laser energy reflected from the interior surfaces of the device under test at a first end and the delayed laser energy from the second direction at a second end for creating two-photon fluorescence between the laser energy reflected from the interior surfaces of the device under test and the delayed laser energy from the second direction and outputting the two-photon fluorescence, wherein the amount of controllable delay is representative of the interior surfaces of the device under test.
In a further aspect of the present invention, and in accordance with its objects and principles, a method for inspecting the interior surfaces of a device under test having a single entry port comprises the steps of launching laser energy into said device under test and into a delay circuit for introducing a controllable delay; receiving light reflected from the interior surfaces of the device into one end of an elongate dye cell; receiving the controllably delayed light into an opposite end of the elongate dye cell; adjusting the controllable delay so that two-photon fluorescence is emitted from a predetermined area of the elongate dye cell; analyzing the controllable delay to discern information about the interior surfaces of the device under test; and outputting the information about the interior surfaces of the device under test.